In recent years, a system in which a large amount of data is used and stored is needed. Accordingly, a network storage system in which a plurality of disk array devices are connected to each other by a storage network has been built.
In such system, critical issues are a data sharing method and a system management method. Generally, these issues can be solved by treating a usable area as a virtual volume. For example, in a system in which a plurality of disk array devices are included, virtualization in which a plurality of magnetic disk devices are viewed as one magnetic disk device is achieved in order to manage the system easily.
For example, a system disclosed in Japanese Patent Application Laid-Open No. 2002-91706 comprises a mapping controller between a host and a storage network or between the storage network and a storage container. The mapping controller makes a virtual disk correspond to a storage container actually used.
A virtual disk system disclosed in Japanese Patent Application Laid-Open No. 1995-152491 converts a logical address of a virtual drive sent from an upper device into a physical address of a physical drive and has a table (virtual drive management table) to judge whether the physical drive corresponding to the logical address exists in a unit. By using the table, the virtual disk system performs a process in the unit when it is judged that the physical drive to be accessed exists in the unit and transfers an access request to an access control circuit of the other unit when it is judged that the physical drive to be accessed exists in the other unit.
As the other related technology, a virtualization device which virtualizes a storage area provided by a storage device is disclosed in Japanese Patent Application Laid-Open No. 2006-209237. An information conversion device which converts logical transfer information into physical transfer information between the upper device and a lower device is disclosed in Japanese Patent Application Laid-Open No. 1994-004450.